Objective To investigate the effects of long-term exposure to fine particulate matter (PM_2.5) on the neurobehavior of male mice.

Methods Thirty-one four-week-old male C57BL/6 J mice were randomly divided into exposure group and control group. The exposure group was exposed to PM_2.5 (mean concentration: 85 μg/m³) in a climate chamber for six consecutive months (8 hrs/day, 30 days/month). The control group was placed in a clean air chamber during the same period. The tail suspension test, open-field test, light-dark box test, rotarod test, and Y-maze test were used to assess the depression-like behavior, motor performance, anxiety-like behavior, and spatial learning and memory of mice after exposure.

Results The open field test showed that total distance traveled, percentage of time spent in the center, percentage of distance traveled in the center, and average speed were (1 699.35±414.54) cm, 8%±5%, 14%±5%, and (4.8±2.5) cm/s, respectively, for the exposure group, and (996.60±370.31) cm, 3%±2%, 9%±4%, and (3.0±1.6) cm/s, respectively, for the control group; the differences between the two groups were statistically significant (P < 0.05). The light-dark box test showed that the number of transitions was significantly different between the exposure group and the control group (P < 0.05), which were (17±4) and (10±6), respectively. No significant differences were found between the two groups in terms of immobility time in the tail-suspension test, time spent on the rod or the speed of the rod in the rotarod test, or spontaneous alternation (%) in the Y-maze test (P>0.05).

Conclusion Long-term exposure to PM_2.5 has a negative influence on the nervous system of mice, which manifests as hyperactivity and reduced anxiety-like behavior.